The fact that animators have to act some scenes to get the exact interpretation in movement or expressions have been a constant trough time. In some cases, production would hire actors/actresses or/and dancers, to make accurate studies in movement sequences.
As many, this is the case in The Boxtrolls scene of Madame Frou Frou´s stage number, one of many examples of intricate character movement in this great LAIKA movie, as the video shows.
“INSIDE LAIKA
Animator Jason Stalman used choreographers, real-life dancers, and LAVs (Live Action Videos) to bring Madame Frou Frou’s dance routine to life for.”